Biomedical subjects

G van Aswegen

Publications and source records attributed to G van Aswegen.

5 recordsLinked to original sources

PubMed1999

Influence of lactation on the prolactin secreting cells of the hypophysis of impala (Aepyceros melampus): an immunocytochemical and computer image analysis study.

Acute stress in the course of wildlife management has been intensively investigated. Chronic stress, on the contrary, has not been researched at all, probably due to the difficulty in measuring it as a result of the overriding effect of the physiological response to the restraining of wild animals. It was therefore decided to evaluate the use of immunocytochemistry, combined with computer image analysis to try and determine the magnitude of the structural changes of various hormone-secreting cells of the hypophysis. Since it was a pilot study to determine whether the combination of immunocytochemistry with computer image analysis could be of value to distinguish between two normally diverse groups, it was decided to compare the relative activity of prolactin secreting cells of lactating and non-lactating impala ewes. After transforming the prolactin immunoreactive area data by log10 to fall inside the parameters for kurtosis and skewness, a significant difference (P < 0.05, 5-% level, 2-tail) with the parametric t-test could be shown between the mean prolactin immunoreactive area of lactating (3.0751 micron 2) and non-lactating (3.0467 micron 2) ewes. However, the Pearson product moment (r = 0.03) showed that this difference may not be important for all practical reasons. This may be due to either sampling errors or limitations of computer image analysis, as it was often difficult to distinguish individual prolactin immunoreactive areas. Furthermore, a significant increase in the total prolactin immunoreactive areas of lactating ewes was also established. This technique, however, could distinguish between the hypophysis of lactating and non-lactating impala ewes, and with further refinement could be a useful tool in determining chronic stress in wildlife populations.

Animals↗

PubMed1996

Putative cardiotoxicity of the venoms of three mamba species.

The venoms of all mamba species are known to contain potent neurotoxins. Some authors suggest that cardiotoxins from mamba venom are responsible for heart failure in envenomated patients. This study was undertaken to come to a better understanding of the mechanisms and possible effects of mamba venom on the hearts of animals. The venoms of three mamba species namely Dendroaspis polylepis, Dendroaspis angusticeps, and Dendroaspis jamesoni were screened for cardiotoxicity by the cardiomyocyte viability test on cardiomyocytes isolated enzymatically from guinea pig ventricle muscle. This analysis was followed by an electrophysiological evaluation of the effects of venoms (from the Dendroaspis species) on cardiac ion channels by employing the whole-cell clamp procedure. In this study the cardiomyocyte viability test indicates differences among the venoms of the three mamba species. The venom of D. jamesoni seems to be the most potent followed by D. angusticeps and then D. polylepis. The whole-cell clamp results indicate that the venoms have no affinity for cardiac potassium channels but have an inhibitory influence on cardiac L-calcium channels. Although this study provides evidence that mamba venoms have a specific effect on isolated myocytes of guinea pig, it is doubtful that it will have a profound influence on a human heart in case of envenomation.

Animals↗

PubMed1996

Immunogold localization and quantification of cellular and subcellular abscisic acid, prior to and during drought stress.

An immunogold labeling procedure and experimental data are presented, which demonstrate that antibodies produced against a bovine serum albumin-abscisic acid conjugate can be used both to characterize the cellular and subcellular localization of abscisic acid (ABA), and to permit quantitative comparisons of this hormone in the subcellular compartments prior to and at times of drought stress. At the control leaf water potential (approximately -0.45 MPa), a quantitatively similar positive labeling pattern was observed in the chloroplasts and apoplast. A twofold drought stress-induced increase in the apoplastic ABA concentration was observed in the drought stressed leaf tissue (i.e., at a leaf water potential of approximately -1.55 MPa), while the ABA concentration in the chloroplasts did not differ from that of the controls. Three histochemical controls and the physiological observations validated the specificity of the procedure. Based on the labeling patterns we observed and literature cited, the validity of the hypothesis that drought stress induces a release of chloroplastic ABA is questioned. We interpreted our results as providing indirect evidence for a drought stress-induced root source origin for the increased apoplastic ABA concentrations.

Abscisic Acid↗

PubMed1989

Developmental profile of chromogranin, hormonal peptides, and 5-hydroxytryptamine in gastrointestinal endocrine cells.

In this immunocytochemical study, we have analyzed the developmental profile and phenotypic expression of the endocrine cell antigens chromogranin, 5-hydroxytryptamine, gastrin/cholecystokinin, cholecystokinin (9-20), somatostatin, somatostatin 28 (1-14), somatostatin cryptic peptide, glucagon, glucagonlike peptides 1 and 2, glicentin, peptide YY, glucose-dependent insulinotropic peptide, secretin, neurotensin, and substance P in human fetal stomach and intestine. All currently identifiable endocrine cell types were detected by 10 wk of gestation. Immunostaining for the endocrine cell marker chromogranin revealed abundant endocrine cells in the earliest specimens (8 wk of gestation) with a relatively higher frequency in both proximal duodenum and distal colon/rectum compared with other areas. Quantification of endocrine cells showed an increase with age that was roughly parallel to the growth of the gut as a whole. These studies show that the diversity of the endocrine component of the gut appears to be established by 10 wk of gestation and that gut activity is preceded by the development of a fully differentiated endocrine component, which may subserve or even initiate the onset of functional maturity.

Antibodies, Monoclonal↗

PubMed1977

Viral hepatitis.

The natural history of and biochemical changes in 27 patients with viral hepatitis are outlined. Analysis is made of the symptomatology and physical signs at the time of presentation as well as a comparison between hepatitis B surface antigen-positive and negative patients. In general, hepatitis B surface antigen-positive patients have a more severe clinical illness as well as greater biochemical derangement and a longer duration of disease.

Adolescent↗